The invention relates to a piston with an encompassing seal, which is seated slidably in a cylindrical receiving bore of a structural part, such as a housing block, and can be acted upon by pressure on at least one end.
Pistons of this kind are used in many forms. In the present invention, this piston is intended primarily for use in a structural part such as a housing block for a hydraulic brake system. In international application WO 91/16220, for instance, a plurality of pistons are supported slidably in suitable receiving bores in a housing block for a hydraulic brake system and can be acted upon by pressure on one end, causing these pistons to slide in the receiving bore counter to the pressure of the spring.
As a rule, such pistons are seated against an inner wall of the receiving bore via a sealing ring, thereby dividing a pressure chamber from a chamber that as a rule is not acted upon by pressure. In this latter chamber, for instance as in WO 91/16220, there is a spring that returns the piston to its outset position if the pressure decreases.
An essential factor for the seal is that it be retained on the outer circumference of the piston and protected against damage. By way of example, the retention can be effected by an annular channel in the piston, but this makes piston manufacture, for instance by injection molding, more difficult. Above all unmolding proves difficult, and burrs are created on the actual. running surface of the piston and on the bearing face for the seal, necessitating post-machining. The seal is also not protected against dirt and chips, for instance from a connecting conduit to a pressure storage chamber, so that damage to the seals and hence leaks can occur.